AMI 186, Инструкции по установке, эксплуатации и обслуживанию

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19
Calibration
Approximate Calibration
released. The level on the sensor when the MAX button is pressed becomes
the 100% level.
Note
If the instrument displayed a 100% reading before a break is observed in the
slope of the level trace, then the MAX calibration point set prior to the current
procedure has interfered. If this occurs, the customer has two options: 1) stop
the procedure, repeatedly enter a value of
120 for C
adj
(see steps 4 and 5 of
the presetting procedure) until the current liquid level display falls below
100%, and then continue the procedure; or 2) continue the liquid transfer
until the liquid level is determined to be 100% by means other than feedback
from the instrument and then pressing the MAX calibration push-button.
6. To achieve a standard calibration of the sensor with the active region located
from the lower hole to one inch below the upper hole, use the level data from
the instrument to recalibrate the MAX point when the percent level
corresponds to one inch below the upper hole. Use the following equation to
determine the percent level at which to reset the MAX calibration point:
where L
active
is the active length of the sensor in inches. This technique can be
used assuming the sensor was built as a standard sensor. If the sensor was
made in a custom configuration, refer to the sensor documentation and/or
drawing or contact AMI.
Example: 20" active length sensor:
When the sensor is calibrated by the closed dewar procedure, the actual length
of calibration will be 21" (distance between the bottom and top holes in the
sensor). When the liquid is 1" below the upper hole, the display will show
95.2% [e.g. 100%
−
(1"/21" x 100%) ]. When the liquid level reaches this
point during usage, push the MAX calibrate button. The instrument and
sensor are now calibrated with a standard active region of 20". The LENGTH
setting of the instrument should also be configured for 20".
7. Proceed to the Operation section for directions for configuring the instrument.
Approximate Calibration
This procedure is the least accurate form of calibration and should be used only when
the aforementioned calibration procedures are not viable. The approximate calibration
method can be used in cases where the sensor cannot be dipped into the target liquid,
the full active length of the sensor cannot be dipped into an open dewar, or both.
Approximate calibration may also be useful for situations where the sensor cannot be
dipped into the target liquid under the expected operating pressure.
MAX
percent
100 100
1
L
active
----------------
– =